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Second gene expression test yields higher positive predictive value for thyroid malignancy
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A gene expression classifier test has a poor positive predictive value for malignancy in thyroid nodules with atypia of undetermined significance; however, a second consecutive gene expression classifier test yielded a higher positive predictive value.
Repeat fine-needle aspiration (FNA) for thyroid nodules with atypia of undetermined significance (AUS) is recommended instead of moving directly to gene expression classifier (GEC) testing, according to researchers.
Carmen V. Villabona, MD, of the department of endocrinology, Cleveland Clinic Florida in Weston, Florida, and colleagues evaluated 119 patients who underwent FNA of thyroid nodules larger than 1 cm with AUS identified from 2012 to 2014. Researchers sought to determine the clinical validity and utility of GEC for evaluation of AUS cytology as well as the performance of ultrasound for predicting malignancy when a nodule is identified as AUS.
Based on initial cytopathology, 48 nodules were sent for GEC, and 27 were classified as GEC suspicious for malignancy. Surgery was performed in 21 of the cases, and had thyroid cancer on histopathology. In 71 cases with AUS cytology on initial FNA, GEC was not performed and patients were sent for a second FNA; 19 of nodule were identified as benign and 52, ranging from 1 to 4 cm in size, were still reported as AUS.
Fourteen (27%) of the cases with reported AUS after second FNA were classified as GEC benign; four had surgical follow-up and three of those were confirmed benign and one malignant. Thirty-eight (73%) of the cases were reported as GEC suspicious for malignancy; 35 underwent, and 32 were confirmed as malignant. A sensitivity of 96% was yielded with GEC correctly identifying 32 of the 35 malignant samples.
There was a positive predictive value of 92% for malignancy for nodules designated AUS on second evaluation that were hypoechoic and solid on ultrasound.
“Our data suggests that proceeding directly to surgery after two AUS cytologies for nodules that are solid and hypoechoic is a reasonable practice given a high yield for malignancy,” the researchers wrote. “Additional assessment with GEC would be helpful in nodules not having these ultrasound characteristics to better exclude malignancy. Also being more cost effective, we suggest repeating a biopsy rather than conducting GEC.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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